Conductive Sleeved Fastener Assembly

ABSTRACT

A conductive sleeved fastener assembly includes an electrically-conductive fastener having a fastener head and a fastener shank extending from the fastener head and an electrically-conductive fastener sleeve receiving the fastener shank of the fastener and a fastener sleeve flange provided on the fastener sleeve and disposed in direct contact with the fastener head of the fastener. A method of preparing a conductive sleeved fastener for use is also disclosed.

TECHNICAL FIELD

The disclosure relates to fasteners for fastening structures to eachother. More particularly, the disclosure relates to a conductive sleevedfastener assembly which provides an electrically-conductive interfacebetween a fastener sleeve and a fastener while maintaining lubricityrequirements.

BACKGROUND

In some aerospace applications, it may be desirable to secure structuresto each other using a fastener. A fastener having a diameter which isgreater than the diameter of a fastener opening provided in thestructures to be secured may be forced into the fastener opening toachieve an interference fit of the fastener in the fastener opening. Alubricant such as cadmium, for example and without limitation, may becoated on the fastener shank to provide the necessary lubricity toinsert the fastener in the fastener opening and maintain conductivitybetween the fastener shank and the structures. In the case of compositestructures and titanium structures, however, it may be desirable to usea sleeved fastener.

In order to reliably install a sleeved fastener into sleeve openingsprovided in the structures, it may be necessary to lubricate the shankof the fastener. In some applications, multiple lubricants may beapplied to the fastener shank to lubricate the fastener shank in thesleeve. The lubricant(s) may be applied to the fastener shank and/or tothe interior surface of the sleeve. The lubricants may electricallyinsulate the fastener from the fastener sleeve. In some applications, itmay be desirable to enhance the electrical conductivity between thefastener and the fastener sleeve.

Therefore, a conductive sleeved fastener assembly which provides anelectrically-conductive interface between a fastener sleeve and afastener while maintaining lubricity requirements may be desirable forsome applications.

SUMMARY

The disclosure is generally directed to a conductive sleeved fastenerassembly. An illustrative embodiment of the sleeved fastener assemblyincludes an electrically-conductive fastener having a fastener head anda fastener shank extending from the fastener head and anelectrically-conductive fastener sleeve receiving the fastener shank ofthe fastener and a fastener sleeve flange provided on the fastenersleeve and disposed in direct contact with the fastener head of thefastener.

The disclosure is further generally directed to the method of preparinga conductive sleeved fastener for use. An illustrative embodiment of theconductive sleeved fastener includes providing a fastener having afastener head, a fastener shank extending from the fastener head, afastener sleeve provided on the fastener shank and a sleeve flange onthe fastener sleeve; applying a lubricant to the fastener shank of thefastener; maintaining the fastener head of the fastener and the sleeveflange of the fastener sleeve devoid of the lubricant; and placing thefastener head of the fastener in direct electrically-conductive contactwith the sleeve flange of the fastener sleeve.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

FIG. 1 is a sectional view of a conductive sleeved fastener assembly inwhich one of a first composite structure and a first metal structure isfastened to one of a second composite structure and a second metalstructure.

FIG. 1A is an enlarged sectional view, taken along section line 1A inFIG. 1.

FIG. 2 is a flow diagram which illustrates an illustrative method ofpreparing a conductive sleeved fastener for use.

FIG. 3 is a flow diagram of an aircraft production and servicemethodology.

FIG. 4 is a block diagram of an aircraft.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the described embodiments or the application anduses of the described embodiments. As used herein, the word “exemplary”or “illustrative” means “serving as an example, instance, orillustration.” Any implementation described herein as “exemplary” or“illustrative” is not necessarily to be construed as preferred oradvantageous over other implementations. All of the implementationsdescribed below are exemplary implementations provided to enable personsskilled in the art to make or use the invention and are not intended tolimit the scope of the invention which is defined by the claims.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,brief summary or the following detailed description.

Referring initially to FIGS. 1 and 1A, an illustrative embodiment of theconductive sleeved fastener assembly, hereinafter assembly, is generallyindicated by reference numeral 1. The assembly 1 is suitable forattaching a first composite structure 20 to a second composite structure21. The assembly 1 may include a generally elongated, cylindrical,electrically-conductive fastener sleeve 8 having an outwardly-extending,annular fastener sleeve flange 9. The fastener sleeve 8 is extendedthrough a bolt opening 23 provided in the first composite structure 20and the second composite structure 21. The fastener sleeve flange 9 ofthe fastener sleeve 8 may engage an outer surface 25 of the firstcomposite structure 20.

An electrically-conductive fastener 2 may include a fastener head 3 anda fastener shank 5 which extends from the fastener head 3. The surfaceof the fastener head 3 may be a bare metal surface without a coating orsolid film lubricant. The fastener shank 5 of the fastener 2 may extendthrough the fastener sleeve 8 and the fastener head 3 may engage thefastener sleeve 9. The fastener head 3 may have a contact surface 4which is disposed in direct engagement with a fastener sleeve contactsurface 10 on the fastener sleeve when the fastener 2 fully engages thefastener sleeve 9. As shown in FIG. 1, a shank portion 5 a of thefastener shank 5 may extend beyond the second composite structure 21 andmay receive a nut 16 which may be tightened against the second compositeor metal structure 21.

As shown in FIG. 1A, wherein the fastener 2 only partially engages thefastener sleeve 9, the fastener shank 5 may have a conductive fastenershank contact surface 6 which may be disposed in direct engagement witha conductive fastener sleeve contact surface 11 on the interior of thefastener sleeve flange 9. A lubricant 12 may be interposed between thecontact interface between the fastener shank 5 and the fastener sleeve 8to facilitate optimal insertion of the fastener shank 5 into thefastener sleeve 8. In some embodiments, the lubricant 12 may include asingle lubricant or any combination of solid film lubricants and/orother lubricants that are suitable for use between the fastener shank 5and the fastener sleeve 8 to sufficiently reduce the installation forcenecessary to insert the fastener shank 5 into the fastener sleeve 8.Cetyl alcohol is one example of a lubricant which may be suitable as thelubricant 12. The lubricant 12 and/or dielectric coatings (not shown)may be omitted from the interface between the fastener head contactsurface 4 and the sleeve contact surface 10 and may additionally beomitted from the interface between the fastener shank contact surface 6and the fastener sleeve contact surface 11. Accordingly, an electricalconductivity pathway may be established between the fastener head 3 andthe fastener sleeve flange 9 at the interface between the fastener headcontact surface 4 and the sleeve contact surface 10. An electricalconductivity pathway may also be also established between the fastenershank 5 and the fastener sleeve 8 at the interface between the fastenershank contact surface 6 and the fastener sleeve contact surface 11. Thismay increase the sparking threshold between the fastener 2 and thefastener sleeve 8 and fastener sleeve flange 9 in the event that anelectrical current is directly applied to the fastener 2 or in the eventthat current travels through the first structure 20 and/or the secondstructure 21. The lubricant 12 may impart electrical resistance betweenthe fastener sleeve 8 and the fastener shank 5.

Referring next to FIG. 2, a flow diagram 200 which illustrates anillustrative method of preparing a conductive sleeved fastener for useis shown. In block 202, a fastener is provided. The fastener may includea fastener head, a fastener shank extending from the fastener head, afastener sleeve provided on the fastener shank and a sleeve flangeprovided on the fastener sleeve. In block 204, one or more lubricantsmay be applied to the fastener shank of the fastener and/or to theinterior surface of the sleeve shank. In some applications, thelubricant(s) may be applied to the entire fastener may be coated orlubricated as selective finishing requires additional work and/or flow.In some embodiments, the lubricants may include a single lubricant orany combination of solid film lubricants and/or other lubricants thatare suitable for use between the fastener shank and the fastener sleeveto sufficiently reduce the installation force necessary to insert thefastener shank into the fastener sleeve. Cetyl alcohol is one example ofa lubricant which may be suitable as the lubricant. The sleeve flange ofthe fastener sleeve may remain devoid of solid film lubricant. In block206, the fastener head and fillet radius of the fastener and the sleeveflange of the fastener sleeve may remain devoid of the lubricants and/ordielectric coatings. In subsequent steps, the fastener sleeve may beextended through registering sleeve openings provided in a firstcomposite structure and a second composite structure and a nut may bethreaded on a threaded shank portion provided on the fastener shank ofthe fastener and tightened. Electrical conductivity pathways may beestablished and the sparking threshold reduced between the fastener headand the sleeve flange of the fastener sleeve and between the filletradius of the fastener and the sleeve flange.

Referring next to FIGS. 3 and 4, embodiments of the disclosure may beused in the context of an aircraft manufacturing and service method 78as shown in FIG. 3 and an aircraft 94 as shown in FIG. 4. Duringpre-production, exemplary method 78 may include specification and design80 of the aircraft 94 and material procurement 82. During production,component and subassembly manufacturing 84 and system integration 86 ofthe aircraft 94 takes place. Thereafter, the aircraft 94 may go throughcertification and delivery 88 in order to be placed in service 90. Whilein service by a customer, the aircraft 94 may be scheduled for routinemaintenance and service 92 (which may also include modification,reconfiguration, refurbishment, and so on).

Each of the processes of method 78 may be performed or carried out by asystem integrator, a third party, and/or an operator (e.g., a customer).For the purposes of this description, a system integrator may includewithout limitation any number of aircraft manufacturers and major-systemsubcontractors; a third party may include without limitation any numberof vendors, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 4, the aircraft 94 produced by exemplary method 78 mayinclude an airframe 98 with a plurality of systems 96 and an interior100. Examples of high-level systems 96 include one or more of apropulsion system 102, an electrical system 104, a hydraulic system 106,and an environmental system 108. Any number of other systems may beincluded. Although an aerospace example is shown, the principles of theinvention may be applied to other industries, such as the automotiveindustry.

The apparatus embodied herein may be employed during any one or more ofthe stages of the production and service method 78. For example,components or subassemblies corresponding to production process 84 maybe fabricated or manufactured in a manner similar to components orsubassemblies produced while the aircraft 94 is in service. Also, one ormore apparatus embodiments may be utilized during the production stages84 and 86, for example, by substantially expediting assembly of orreducing the cost of an aircraft 94. Similarly, one or more apparatusembodiments may be utilized while the aircraft 94 is in service, forexample and without limitation, to maintenance and service 92.

Although the embodiments of this disclosure have been described withrespect to certain exemplary embodiments, it is to be understood thatthe specific embodiments are for purposes of illustration and notlimitation, as other variations will occur to those of skill in the art.

1-20. (canceled)
 21. A method of connecting two composite structures,the method comprising: positioning an electrically-conductive sleevewithin an opening in a first composite structure, theelectrically-conductive sleeve extending into an opening in a firstcomposite structure; engaging an outer surface of the first compositestructure with a flange of the electrically-conductive sleeve; applyinga lubricant to a shank of an electrically-conductive fastener, the shankextending from a head of the electrically-conductive fastener; insertingthe shank of the electrically-conductive fastener into theelectrically-conductive sleeve; and establishing an electricalconductivity pathway between the electrically-conductive fastener andthe electrically-conductive sleeve.
 22. The method of claim 21, whereinestablishing an electrical conductivity pathway further comprisesengaging a contact surface on the electrically-conductive fastener witha contact surface on the electrically-conductive sleeve.
 23. The methodof claim 21, further comprising threading a nut onto the shank of theelectrically-conductive fastener.
 24. The method of claim 21, furthercomprising maintaining the head of the electrically-conductive fastenerand the flange of the electrically-conductive fastener sleeve devoid ofthe lubricant.
 25. The method of claim 24, wherein maintaining the headof the electrically-conductive fastener and the flange of theelectrically-conductive fastener sleeve devoid of the lubricant furthercomprises maintaining a fillet radius of the electrically-conductivefastener devoid of the lubricant.
 26. The method of claim 21, whereinapplying the lubricant to the shank of the electrically-conductivefastener further comprises applying a solid film lubricant to the shankof the electrically-conductive fastener.
 27. The method of claim 21,wherein applying the lubricant to the shank of theelectrically-conductive fastener further comprises applying a firstlubricant to the shank and applying a second lubricant to the shank. 28.The method of claim 27, wherein the first lubricant is cetyl alcohol andthe second lubricant is a solid film.
 29. A method of attaching a firstcomposite structure to a second composite structure comprising:positioning an electrically-conductive fastener sleeve within a boltopening in a first composite structure and a bolt opening in a secondcomposite structure; engaging an outer surface of the first compositestructure with a flange of the electrically-conductive sleeve; applyinga lubricant to a shank of an electrically-conductive fastener, the shankextending from a head of the electrically-conductive fastener; insertingthe shank of the electrically-conductive fastener into theelectrically-conductive sleeve, wherein a portion of the shank of theelectrically-conductive fastener extends beyond the second compositestructure; and establishing an electrical conductivity pathway betweenthe electrically-conductive fastener and the electrically-conductivesleeve.
 30. The method of claim 29, wherein establishing an electricalconductivity pathway further comprises engaging a contact surface of theelectrically-conductive fastener with a contact surface on theelectrically-conductive sleeve.
 31. The method of claim 30, wherein thecontact surface of the electrically-conductive fastener is on the headof the electrically-conductive fastener.
 32. The method of claim 30,wherein the contact surface of the electrically-conductive fastener ison a fillet radius of the fastener shank.
 33. The method of claim 29,wherein establishing an electrical conductivity pathway furthercomprises engaging a contact surface on the head of theelectrically-conductive fastener with a contact surface on theelectrically-conductive sleeve and engaging a contact surface on afillet radius of the fastener shank with a contact surface on theelectrically-conductive sleeve.
 34. The method of claim 29, furthercomprising threading a nut onto the portion of the shank of theelectrically-conductive fastener that extends beyond the secondcomposite structure.
 35. The method of claim 29, further comprisingmaintaining the head of the electrically-conductive fastener and theflange of the electrically-conductive fastener sleeve devoid of thelubricant.
 36. The method of claim 35, wherein maintaining the head ofthe electrically-conductive fastener and the flange of theelectrically-conductive fastener sleeve devoid of the lubricant furthercomprises maintaining a fillet radius of the electrically-conductivefastener devoid of the lubricant.
 37. The method of claim 29, whereinapplying the lubricant to the shank of the electrically-conductivefastener further comprises applying a solid film lubricant to the shankof the electrically-conductive fastener.
 38. The method of claim 29,wherein applying the lubricant to the shank of theelectrically-conductive fastener further comprises applying a firstlubricant to the shank and applying a second lubricant to the shank. 39.The method of claim 38, wherein the first lubricant is cetyl alcohol andthe second lubricant is a solid film.